The first and perhaps most significant reason for skepticism is that there are far fewer religious liberals today than there were a generation ago. Nearly four in 10 (38 percent) liberals are religiously unaffiliated today, more than double the percentage of the 1990s, according to data from the General Social Survey. In part, the liberal mass migration away from religion was a reaction to the rise of the Christian right. Over the last couple decades, conservative Christians have effectively branded religious activism as primarily concerned with upholding a traditional vision of sexual morality and social norms. That conservative religious advocacy contributed to many liberals maintaining an abiding suspicion about the role that institutional religion plays in society and expressing considerable skepticism of organized religion generally. Only 30 percent of liberals report having a great deal or quite a lot of confidence in organized religion. Half say that religion's impact on society is more harmful than helpful.

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Another challenge confronting the progressive religious movement is the yawning generational divide in religious identity. Young liberals today are simply not that religious. Nearly half (49 percent) of liberals under 30 are religiously unaffiliated, according to the General Social Survey, which is more than the number who belong to all Christian denominations combined. Only 22 percent of liberal seniors are unaffiliated, while the overwhelming majority identify as religious. Your average left-leaning Christian is pushing 50. Coaxing young progressives to join a movement that would require them to reset their approach to religion is no small undertaking.

Read the whole thing.

I would add this to the critique: liberal religion is simply insufficiently substantive to hold most people, particularly across generations. It is also true that milquetoast moderate bourgeois Christianity isn't going to hold people either, but that's true for the same reason that liberal Christianity won't do it either. If liberalizing religion to make it a better fit for post-Christian modernity were the answer, the Protestant mainline would be booming now. I don't doubt that there are many true believers within liberal Christian circles -- some of them comment here -- but I do doubt that most of them will be able to pass that faith on in the same way to their children. To be sure, it's not easy for any of us, not in these times. But the problem, I believe, is much more serious for religious liberals.

Cox, the researcher, explains why: because younger people who identify as liberal are far less likely to be religious.

The late Cardinal George of Chicago once said, explaining why liberal Catholicism is a dead end:

Behind the crisis of visible authority or governance in a liberal church lies a crisis of truth. In a popular liberal society, freedom is the primary value and the government is not supposed to tell its citizens how to think. The cultural fault line lies in a willingness to sacrifice even the gospel truth in order to safeguard personal freedom construed as choice. Using sociology of knowledge and the hermeneutics of suspicion, modern liberals interpret dogmas which affront current cultural sensibilities as the creation of celibate males eager to keep a grasp on power rather than as the work of the Holy Spirit guiding the successors of the Apostles. The bishops become the successors of the Sanhedrin and the church, at best, is the body of John the Baptist, pointing to a Jesus not yet risen from the dead and, therefore, a role model or prophet but not a savior. Even Jesus' being both male and celibate is to be forgotten or denied once the risen Christ can be reworked into whomever or whatever the times demand. Personal experience becomes the criterion for deciding whether or not Jesus is my savior, a point where liberal Catholics and conservative Protestants seem to come to agreement, even if they disagree on what salvation really means. Liberal culture discovers victims more easily than it recognizes sinners; and victims don't need a savior so much as they need to claim their rights.

All this is not only a dead end, it is a betrayal of the Lord, no matter the good intentions of those espousing these convictions. The call to personal conversion, which is at the heart of the gospel, has been smothered by a pillow of accommodation. The project for a liberal Catholic church is as unoriginal as the project for a liberal reinterpretation of the mission for the church. A church, all of whose ministries, construed only functionally, are open to any of the baptized; a church unwilling to say that all homosexual genital relations are morally wrong; a church which at least makes some allowance for abortion when necessary to assure a mother's freedom; a church accepting contraception as moral within marriage and prudent outside of marriage; a church willing to admit the sacramentally married to a second marriage in complete sacramental communion; a church whose teaching has to stand the acid test of modern criticism and personal acceptance in order to have not just credibility but legitimacy--there is nothing new in all this. It already exists, but outside the Catholic church.

More broadly, we could say that many of the things liberal Christians believe in and advocate, in contradiction to normative Christian orthodoxy, already exist outside the church, period. Liberal Christianity often appears as a somewhat desperate attempt to sanctify modern beliefs. More to the point, Philip Rieff had the number of liberal Christianity, saying in 1966's The Triumph of the Therapeutic that Christian pastors and priests would desperately but futilely try to update their doctrines to accommodate the modern world -- especially regarding sexuality -- but would fail, in part because there really is no credible way to do this. The testimony of the Bible is simply overwhelmingly against what they want to do. Rieff didn't say this, but I will: the labor one has to accomplish to "liberate" Christianity from traditional Biblical sexual ethics is so immense that you have to tear down the entire castle to free the prisoner from the dungeon.

Rieff's theory of culture explains why liberal Christianity has no future. Here is a longish Rieff passage explaining his theory. In a nutshell, Rieff says that culture, of which religion is a part, is defined by what it prescribes and what it forbids. A culture based on knocking down taboos, on forbidding to forbid, is an anti-culture. It cannot do what a culture must do. Aside from advocating for the legitimization of homosexual desire and the approbation of sexual permissiveness, what does liberal Christianity really stand for? If it amounts to just the desiring individual and the sacrosanct quality of his own personal interpretation of Scripture and the Christian tradition, then liberal religion cannot do anything other than dissolve.

Note well, religious conservatives: if the essence of your religious conservatism is merely a reflection of your social milieu, your religion will dissolve in your children's generation too. I know a number of older folks who might be fairly described as religious conservatives, but who have failed to transmit the faith to their offspring. Of course this is not a matter of data transfer, but rather a matter of cultivation. Not every plant in a garden will flourish, because they are organic, not mechanisms. So it is with human beings. Nevertheless, I am convinced that many, many conservatives who happen to be Christian are far too trusting in the habits of culture to pass on the faith. Given the post-Christian -- and increasingly anti-Christian -- qualities of the broader culture, if you are not affirmatively and meaningfully traditionalist in your approach to and practice of faith, your kids are more likely than not to lose the faith.

Let me end by reaching out to middle-aged and older readers who identify as liberal Christians, or as religious liberals within non-Christian traditions. Are your adult children practicing the faith? Why or why not? Do you think the way you brought them up in the faith had anything to do with the decision they have made? I'm not accusing you; I just want to understand this phenomenon.

UPDATE: A reader writes to recount a conversation with a senior leader in a Mainline Protestant church, who said, ruefully, that even the healthiest liberal congregations "are like mules: they're perfectly healthy, but they can't reproduce."

UPDATE.2: Reader Jeremy Hickerson comments:

Here's an example from my church that shows Rod is right to say that mainline or liberal Christianity is straying far from the faith. I give it out of honesty and dismay, and I'm still going to stay part of my church, but it shook me and made me question whether I did wrong by my kids by bringing them up in this church. I posted earlier that one of my two daughters is practicing the faith, and I have seen a number of children grow up in this church and stay in the faith. The thing that drew me and my wife to the church in the first place was the involvement of youth in the worship service the first time we visited. And my experience growing up in the evangelical church rules out that branch of Christianity for my, I have no regrets about not bringing up my kids in an evangelical church.

Here's what happened yesterday. I was teaching an adult Sunday School class. In Methodism, we have what we call the "Wesley Quadrilateral". This is 4 tools to arrive at decisions about doctrine, practice, etc. They are Scripture (which should be given the most weight of the four), Tradition, Reason, and Experience. A few weeks ago someone had brought this up in the S.S. class and I had asked if there were any limits to what we could change using the Quadrilateral. The general response was that there were no limits. Yesterday I said that the limits, the core that we could not touch were:

1) Humans are sinful
2) Jesus is God and human
3) Jesus died to pay for our sins
4) Jesus rose from the dead

There was a big uproar and massive disagreement with this. One person spoke up and said, look, Jeremy's not crazy, this is basically just part of the apostle's creed. I pointed out that we had just recited this in the service a half hour ago. Another person said that my list of four was ecumenical enough that Catholics, Orthodox, Evangelicals, would all agree with it. So out of the 15 to 20 in the class, 2 agreed and the rest didn't or didn't say anything.

This class is very close, and they are all my close friends. We have basically raised each others kids over the years. This is a great group. But it shook me to the core.

What really bothered me was not so much that people didn't themselves believe the core of Christianity. I'm not surprised that might be the case -- a big strength our church is accepting people where they are at. If they want to come be part, we welcome them. This follows the example of Jesus when he was on earth. What bothered me was that they felt it was out of place and wrong for a church to stand up for the faith it has in its doctrinal statement. Like they were surprised that this sort of thing would be said at a church. I thought they knew we were a church.

And there you have it. These days, a congregation that is not affirmatively orthodox in its theology will become de facto liberal ... and then will evaporate.

The religious liberal Daniel Schultz gives a decent definition of the difference between religious conservatives and religious liberals:

Speaking in very broad terms, liberals see faith as giving them ethics, rather than a universal morality. That is, religious belief provides moral guidelines, but these still have to be applied to individual situations, with quite a bit of room left for diverse outcomes. This makes sense if you stop to think about it: if the world you live in is pluralistic, you accommodate different possible answers to the same questions. But if you live in a culture with more agreement on what God's will is and how it should be applied, you're more likely to see that as universal. (Again, this is very broad, and it's possible to make too much of the distinctions.)

When liberals think about morality, then, they see a heuristic, not a law.

I would rephrase it this way -- again, speaking very broadly: Religious liberals regard Scripture and Tradition as suggestions, perhaps ideals, but reserve to themselves the right to re-interpret in context of their own time and place, and according to their own needs and desires. Religious conservatives regard Scripture and Tradition as authoritative, and disclosing eternal moral and theological truths that bind human understanding and conduct. Another way to look at it: religious liberals think of religion as primarily what Man says about God, while religious conservatives think of religions as primarily what God says about Man.

There will be no religious left in the long term because the religious left, as it is currently constituted, doesn't even believe in its own religion.